This disclosure relates to an active clearance control system and method for a gas turbine engine. More particularly, the disclosure relates to controlling a temperature of a structural member, such as a case, to control the clearance between the case and a blade.
Gas turbine engine blades are housed within structural members, such as cases, having annular flanges that are secured to one another at a joint by fasteners. In one example, the case may support a blade outer air seal that is arranged radially outwardly from tips of the blades. A clearance is provided between the blade outer air seal and the tips. This clearance affects the blade tip wear as well as the efficiency of the fluid flowing through the blades.
It may be desirable to control the clearance between the case and the blades. One example passive arrangement has used a heat shield secured over a pair of flanges, which insulates the cases from the hotter environment external to the cases. Another example arrangement provides a blade outer air seal having a hollow cavity that is provided fluid. Cooling fluid from the cavity is supplied to impingement holes that provide the cooling fluid to a back side of the blade outer air seal. This cooling fluid enters the blade flow path, which may be undesired.